New shadow champion

I was thinking that an idea of a new shadow based champion could be a student of Shen that betrays Shen and aids Kayn to help Kayn kill Zed while the student wants to kill Shen to take over his clan. That can be part of the lore. The power he harvests is similar to Shen and Kayn's ult. Instead of teleporting on a team mate to provide a shield and teleport into a team fight. He can lock onto an ally champion who has a dash or engage. After a few seconds after being locked on a team mate while being untargettable. AOE damage is done to whoever is around a decent and fair radius. It's basically like Shen's ult except it does damage and possibly heals the champion he's locked on instead of dealing damage like how Kayn does. I'd like more thoughts on this for balancing....this champion also could be a female ninja or something.